U.S. patent application number 16/486489 was filed with the patent office on 2019-11-28 for pneumatic tire.
The applicant listed for this patent is The Yokohama Rubber Co., LTD.. Invention is credited to Hiraku Kouda, Tatsuro Shinzawa, Takayuki Shiraishi, Takanori Uemura.
Application Number | 20190359009 16/486489 |
Document ID | / |
Family ID | 63170299 |
Filed Date | 2019-11-28 |
United States Patent
Application |
20190359009 |
Kind Code |
A1 |
Uemura; Takanori ; et
al. |
November 28, 2019 |
Pneumatic Tire
Abstract
In a pneumatic tire, a sipe includes an edge on a leading side
and an edge on a trailing side; the edge on the leading side and
the edge on the trailing side each include a chamfered portion
shorter than a sipe length of the sipe; a non-chamfered region in
which other chamfered portions are not present is provided at
portions facing the chamfered portions of the sipe; and for all
chamfered portions, including at least the chamfered portions of
the sipe, formed on grooves other than main grooves, a total
projected area A.sub.IN of the chamfered portions located on a
vehicle mounting inner side and a total projected area A.sub.OUT of
the chamfered portions located on a vehicle mounting outer side
satisfy a relationship A.sub.IN>A.sub.OUT.
Inventors: |
Uemura; Takanori;
(Hiratsuka-shi, Kanagawa, JP) ; Shiraishi; Takayuki;
(Hiratsuka-shi, Kanagawa, JP) ; Kouda; Hiraku;
(Hiratsuka-shi, Kanagawa, JP) ; Shinzawa; Tatsuro;
(Hiratsuka-shi, Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Yokohama Rubber Co., LTD. |
|
|
|
|
|
Family ID: |
63170299 |
Appl. No.: |
16/486489 |
Filed: |
December 22, 2017 |
PCT Filed: |
December 22, 2017 |
PCT NO: |
PCT/JP2017/046212 |
371 Date: |
August 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 11/03 20130101;
B60C 11/1204 20130101; B60C 11/1259 20130101; B60C 2011/0339
20130101; B60C 11/1272 20130101; B60C 11/12 20130101; B60C 11/1392
20130101 |
International
Class: |
B60C 11/13 20060101
B60C011/13; B60C 11/12 20060101 B60C011/12 |
Claims
1. A pneumatic tire with a designated mounting direction with
respect to a vehicle, comprising: in a tread portion, main grooves
extending in a tire circumferential direction; and a sipe extending
in a tire lateral direction disposed in ribs defined by the main
grooves; wherein the sipe comprises an edge on a leading side and
an edge on a trailing side; the edge on the leading side and the
edge on the trailing side each comprise a chamfered portion shorter
than a sipe length of the sipe; a non-chamfered region in which
other chamfered portions are not present is provided at portions
facing the chamfered portions of the sipe; and for all chamfered
portions, comprising at least the chamfered portions of the sipe,
formed on grooves other than the main grooves, a total projected
area A.sub.IN of the chamfered portions located on a vehicle
mounting inner side and a total projected area A.sub.OUT of the
chamfered portions located on a vehicle mounting outer side satisfy
a relationship A.sub.IN>A.sub.OUT.
2. The pneumatic tire according to claim 1, wherein a maximum depth
x (mm) of the sipe and a maximum depth y (mm) of the chamfered
portions satisfy a relationship
x.times.0.1.ltoreq.y.ltoreq.x.times.0.3+1.0; and a sipe width of
the sipe is constant in a range from an end portion located on an
inner side in a tire radial direction of the chamfered portion to a
groove bottom of the sipe.
3. The pneumatic tire according to claim 1, wherein the total
projected area A.sub.IN of the chamfered portions located on the
vehicle mounting inner side and the total projected area A.sub.OUT
of the chamfered portions located on the vehicle mounting outer
side satisfy a relationship
3%.ltoreq.(A.sub.IN-A.sub.OUT)/A.sub.IN.times.100%.ltoreq.50%.
4. The pneumatic tire according to claim 1, wherein the sipe is
disposed in two or more ribs of the ribs defined by the main
grooves.
5. The pneumatic tire according to claim 4, wherein the all
chamfered portions are configured by the chamfered portion of the
sipe.
6. The pneumatic tire according to claim 2, wherein the total
projected area A.sub.IN of the chamfered portions located on the
vehicle mounting inner side and the total projected area A.sub.OUT
of the chamfered portions located on the vehicle mounting outer
side satisfy a relationship
3%.ltoreq.(A.sub.IN-A.sub.OUT)/A.sub.IN.times.100%.ltoreq.50%.
7. The pneumatic tire according to claim 6, wherein the sipe is
disposed in two or more ribs of the ribs defined by the main
grooves.
8. The pneumatic tire according to claim 7, wherein the all
chamfered portions are configured by the chamfered portion of the
sipe.
Description
TECHNICAL FIELD
[0001] The present technology relates to a pneumatic tire and
particularly relates to a pneumatic tire with a designated vehicle
mounting direction that can provide improved steering stability
performance on dry road surfaces and improved steering stability
performance on wet road surfaces in a compatible manner and further
provide enhanced noise performance by devising a sipe chamfer
shape.
BACKGROUND ART
[0002] In the related art, in a tread pattern of a pneumatic tire,
a plurality of sipes are formed in a rib defined by a plurality of
main grooves. By providing such sipes, drainage properties are
ensured, and steering stability performance on wet road surfaces is
exhibited. However, when a large number of sipes are disposed in a
tread portion in order to improve the steering stability
performance on wet road surfaces, the rigidity of the ribs
decreases, which has the disadvantage that steering stability
performance on dry road surfaces deteriorates. Additionally, when a
large number of sipes are disposed in the tread portion, it is
difficult to achieve noise performance (reduced noise) and steering
stability performance on wet road surfaces in a compatible manner
because the popping sound and the pattern noise when running are
emitted to the outside of the vehicle and noise of the tire tends
to increase.
[0003] Various pneumatic tires have been proposed in which sipes
are formed in a tread pattern and chamfered (for example, see Japan
Unexamined Patent Publication No. 2013-537134). When the sipes are
formed and chamfered, edge effects may be lost depending on the
shape of the chamfers, and depending on the dimensions of the
chamfers, improvement of steering stability performance on dry road
surfaces and improvement of steering stability performance on wet
road surfaces may be insufficient.
SUMMARY
[0004] The present technology provides a pneumatic tire with a
designated vehicle mounting direction that can provide improved
steering stability performance on dry road surfaces and improved
steering stability performance on wet road surfaces in a compatible
manner and further provide enhanced noise performance by devising a
sipe chamfer shape.
[0005] A pneumatic tire according to an embodiment of the present
technology is a pneumatic tire with a designated mounting direction
with respect to a vehicle, including:
[0006] in a tread portion, main grooves extending in a tire
circumferential direction; and
[0007] a sipe extending in a tire lateral direction disposed in
ribs defined by the main grooves; wherein
[0008] the sipe includes an edge on a leading side and an edge on a
trailing side;
[0009] the edge on the leading side and the edge on the trailing
side each include a chamfered portion shorter than a sipe length of
the sipe;
[0010] a non-chamfered region in which other chamfered portions are
not present is provided at portions facing the chamfered portions
of the sipe; and
[0011] for all chamfered portions, including at least the chamfered
portions of the sipe, formed on grooves other than the main
grooves, a total projected area A.sub.IN of the chamfered portions
located on a vehicle mounting inner side and a total projected area
A.sub.OUT of the chamfered portions located on a vehicle mounting
outer side satisfy a relationship A.sub.IN>A.sub.OUT.
[0012] In an embodiment of the present technology, the pneumatic
tire has a designated mounting direction with respect to a vehicle
and includes sipes that extend in the tire lateral direction in
ribs defined by the main grooves. The chamfered portion that is
shorter than the sipe length of the sipe is provided on each of the
edge on the leading side and the edge on the trailing side of the
sipe, and the non-chamfered regions in which other chamfered
portions are not present are disposed at the portions facing the
chamfered portions of the sipe. Thus, the drainage effect can be
improved with the chamfered portions, and a water film can be
effectively removed by the edge effect in the non-chamfered
regions. As a result, the steering stability performance on wet
road surfaces can be greatly improved. Moreover, the chamfered
portion and the non-chamfered region are disposed alongside each
other on the edge on the leading side and the edge on the trailing
side in this manner. Thus, the effect of enhancing wet performance
as described above when braking and driving can be maximally
achieved. Additionally, compared to a known chamfered sipe, the
chamfered area can be minimized, so the steering stability
performance on dry road surfaces can be improved. As a result, the
steering stability performance on dry road surfaces and the
steering stability performance on wet road surfaces can be improved
in a compatible manner. Furthermore, the vehicle mounting outer
side is a large contributor to noise performance. Thus, for all the
chamfered portions, including at least the chamfered portions of
the sipes, which are chamfered portions formed on grooves other
than the main grooves, by the total projected area A.sub.OUT of the
chamfered portions located on the vehicle mounting outer side being
relatively small, the ground contact pressure on the vehicle
mounting outer side can be reduced, which leads to a reduction in
noise generated when running. As a result, the steering stability
performance on dry road surfaces, the steering stability
performance on wet road surfaces, and noise performance can be
enhanced in a well-balanced manner.
[0013] In an embodiment of the present technology, preferably a
maximum depth x (mm) of the sipe and a maximum depth y (mm) of the
chamfered portions satisfy a relationship of Formula (1); and
[0014] a sipe width of the sipe is constant in a range from an end
portion located on an inner side in a tire radial direction of the
chamfered portion to a groove bottom of the sipe. In this way,
compared to a known chamfered sipe, the chamfered area can be
minimized, so the steering stability performance on dry road
surfaces can be improved. As a result, the steering stability
performance on dry road surfaces and the steering stability
performance on wet road surfaces can be improved in a compatible
manner.
x.times.0.1.ltoreq.y.ltoreq.x.times.0.3+1.0 (1)
[0015] In an embodiment of the present technology, the total
projected area A.sub.IN of the chamfered portions located on the
vehicle mounting inner side and the total projected area A.sub.OUT
of the chamfered portions located on the vehicle mounting outer
side preferably satisfy Formula (2). In this way, an effect of
suppressing noise can be obtained and both the steering stability
performance on dry road surfaces and the steering stability
performance on wet road surfaces can be enhanced. More preferably,
the range is from 10% to 30%.
3%.ltoreq.(A.sub.IN-A.sub.OUT)/A.sub.IN.times.100%.ltoreq.50%
(2)
[0016] In an embodiment of the present technology, preferably the
sipe is disposed in two or more ribs of the ribs defined by the
main grooves. In this way, the steering stability performance on
dry road surfaces and the steering stability performance on wet
road surfaces can be enhanced in a well-balanced manner.
[0017] In an embodiment of the present technology, preferably, the
all chamfered portions are configured by the chamfered portion of
the sipe. In this way, the steering stability performance on dry
road surfaces and the steering stability performance on wet road
surfaces can be enhanced in a well-balanced manner.
[0018] In the present technology, "projected area of the chamfered
portion" is the area measured when the chamfered portion is
projected in a normal line direction of the road contact surface of
the tread portion.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a meridian cross-sectional view illustrating a
pneumatic tire according to an embodiment of the present
technology.
[0020] FIG. 2 is a plan view illustrating an example of a tread
portion of a pneumatic tire according to an embodiment of the
present technology.
[0021] FIG. 3 is a perspective view illustrating a portion of a
tread portion of a pneumatic tire according to an embodiment of the
present technology.
[0022] FIG. 4 is a plan view illustrating a portion of a tread
portion of a pneumatic tire according to an embodiment of the
present technology.
[0023] FIG. 5 is a plan view illustrating a sipe and a chamfered
portion thereon formed in the tread portion of FIG. 4.
[0024] FIG. 6 is a cross-sectional view taken along line X-X in the
direction of the arrow in FIG. 4.
[0025] FIG. 7 is a plan view illustrating a modified example of a
tread portion of a pneumatic tire according to an embodiment of the
present technology.
[0026] FIG. 8 is a plan view illustrating another modified example
of a sipe and chamfered portions thereon of a pneumatic tire
according to an embodiment of the present technology.
[0027] FIGS. 9A and 9B are plan views illustrating another modified
example of a sipe and chamfered portions thereon of a pneumatic
tire according to an embodiment of the present technology.
[0028] FIG. 10 is a cross-sectional view taken along line Y-Y in
the direction of the arrow of FIG. 4.
DETAILED DESCRIPTION
[0029] Configurations of embodiments of the present technology are
described in detail below with reference to the accompanying
drawings. In FIGS. 1 and 2, CL denotes the tire center line.
[0030] As illustrated in FIG. 1, a pneumatic tire according to an
embodiment of the present technology has a designated mounting
direction with respect to a vehicle. "IN" indicates the side inward
of the tire center line CL with respect to the vehicle when the
tire is mounted on the vehicle (hereinafter referred to as "vehicle
mounting inner side"), and "OUT" indicates the side outward of the
tire center line CL with respect to the vehicle when the tire is
mounted on the vehicle (hereinafter referred to as "vehicle
mounting outer side"). As illustrated in FIG. 1, the pneumatic tire
includes an annular tread portion 1 extending in the tire
circumferential direction, a pair of sidewall portions 2, 2
disposed on both sides of the tread portion 1, and a pair of bead
portions 3, 3 disposed inward of the sidewall portions 2 in the
tire radial direction.
[0031] A carcass layer 4 is mounted between the pair of bead
portions 3, 3. The carcass layer 4 includes a plurality of
reinforcing cords extending in the tire radial direction and is
folded back around bead cores 5 disposed in each of the bead
portions 3 from a tire inner side to a tire outer side. A bead
filler 6 having a triangular cross-sectional shape formed from
rubber composition is disposed on the outer circumference of the
bead core 5.
[0032] A plurality of belt layers 7 are embedded on the outer
circumferential side of the carcass layer 4 in the tread portion 1.
The belt layers 7 each include a plurality of reinforcing cords
that are inclined with respect to the tire circumferential
direction, with the reinforcing cords of the different layers
arranged in a criss-cross manner. In the belt layers 7, the
inclination angle of the reinforcing cords with respect to the tire
circumferential direction ranges from, for example, 10.degree. to
40.degree.. Steel cords are preferably used as the reinforcing
cords of the belt layers 7. To improve high-speed durability, at
least one belt cover layer 8, formed by arranging reinforcing cords
at an angle of, for example, not greater than 5.degree. with
respect to the tire circumferential direction, is disposed on an
outer circumferential side of the belt layers 7. Nylon, aramid, or
similar organic fiber cords are preferably used as the reinforcing
cords of the belt cover layer 8.
[0033] Note that the tire internal structure described above
represents a typical example for a pneumatic tire, and the
pneumatic tire is not limited thereto. FIG. 2 illustrates an
example of a tread portion of a pneumatic tire according to an
embodiment of the present technology. Four main grooves 9 extending
in the tire circumferential direction are formed in a tread portion
1. The main grooves 9 includes a pair of inner main grooves 9A, 9A
located on both sides of the tire center line CL and a pair of
outer main grooves 9B, 9B located on the outermost side in the tire
lateral direction. Ribs 10 are defined in the tread portion 1 by
the four main grooves 9. The ribs 10 include a center rib 100A
located on the tire center line CL, a pair of intermediate ribs
100B, 100C located outward of the center rib 100A in the tire
lateral direction, and a pair of shoulder ribs 100D, 100E located
outward of the intermediate ribs 100B, 100C in the tire lateral
direction.
[0034] Sipes 11 including a pair of chamfered portions 12 are
formed in each of the center rib 100A and the intermediate ribs
100B, 100C. The sipes 11 includes a sipe 110A disposed in the
center rib 100A and sipes 110B, 110C disposed in each of the
intermediate ribs 100B, 100C. The chamfered portions 12 include a
chamfered portion 120A formed on the sipe 110A, a chamfered portion
120B formed on the sipe 110B, and a chamfered portion 120C formed
on the sipe 110C.
[0035] The sipes 110A are inclined in the same direction with
respect to the tire lateral direction and are formed at intervals
in the tire circumferential direction in the center rib 100A. One
end of the sipe 110A communicates with the inner main groove 9A,
and the other end terminates within the center rib 100A. That is,
the sipe 110A is a semi-closed sipe.
[0036] The sipes 110B are inclined in the same direction with
respect to the tire lateral direction and are formed at intervals
in the tire circumferential direction in the intermediate rib 100B.
One end of the sipe 110B communicates with the inner main groove
9A, and the other end communicates with the outer main groove 9B.
That is, the sipe 110B is an open sipe. The sipes 110C are inclined
in the same direction with respect to the tire lateral direction
and are formed at intervals in the tire circumferential direction
in the intermediate rib 100C. One end of the sipe 110C terminates
within the intermediate rib 100C, and the other end communicates
with the outer main groove 9B. That is, the sipe 110C is a
semi-closed sipe.
[0037] Lug grooves 200 that do not communicate with the outer main
groove 9B extend in the tire lateral direction, are inclined in the
same direction with respect to the tire lateral direction, and are
formed at intervals in the tire circumferential direction in the
shoulder ribs 100D, 100E. The lug grooves 200 include lug grooves
200A formed in the shoulder rib 100D and lug grooves 200B formed in
the shoulder rib 100E.
[0038] FIGS. 3 to 6 illustrate a portion of a tread portion of a
pneumatic tire according to an embodiment of the present
technology. In FIGS. 3 to 5, Tc indicates the tire circumferential
direction and Tw indicates the tire lateral direction. As
illustrated in FIG. 3, the ribs 10 include the sipes 11 extending
in the tire lateral direction and blocks 101 defined by the sipes
11. The blocks 101 are provided side by side in the tire
circumferential direction. The sipes 11 are narrow grooves having a
groove width of 1.5 mm or less.
[0039] As illustrated in FIG. 4, the sipes 11 have an overall shape
that is curved and are formed in the rib 10 at intervals in the
tire circumferential direction. The sipe 11 includes an edge 11A on
the leading side with respect to a rotation direction R and an edge
11B on the trailing side with respect to the rotation direction R.
The chamfered portions 12 are formed on the edge 11A on the leading
side and the edge 11B on the trailing side.
[0040] The chamfered portions 12 includes a chamfered portion 12A
on the leading side with respect to the rotation direction R and a
chamfered portion 12B on the trailing side with respect to the
rotation direction R. At portions facing the chamfered portions 12,
non-chamfered regions 13 in which other chamfered portions are not
present are provided. In other words, a non-chamfered region 13B on
the trailing side with respect to the rotation direction R is
provided at a portion facing the chamfered portion 12A, and a
non-chamfered region 13A on the leading side with respect to the
rotation direction R is provided at a portion facing the chamfered
portion 12B. The chamfered portion 12 and the non-chamfered region
13 in which other chamfered portions are not present are disposed
adjacent to one another on the edge 11A on the leading side and the
edge 11B on the trailing side of the sipe 11 in this manner.
[0041] As illustrated in FIG. 5, the lengths of the sipe 11 and the
chamfered portions 12A, 12B in the tire lateral direction are
defined as a sipe length L and chamfer lengths L.sub.A, L.sub.B,
respectively. The sipe length L and the chamfer lengths L.sub.A,
L.sub.B are lengths in the tire lateral direction from one end
portion to the other end portion for each of the sipes 11 and the
chamfered portions 12A, 12B. The chamfer lengths L.sub.A, L.sub.B
of the chamfered portions 12A, 12B are formed shorter than the sipe
length L of the sipe 11.
[0042] FIG. 6 is a view orthogonal to the extension direction of
the sipe, with the tread portion 1 cut away in the vertical
direction. As illustrated in FIG. 6, the maximum depth of the sipe
11 is x (mm) and the maximum depth of the chamfered portion 12 is y
(mm), and the sipe 11 and the chamfered portion 12 are formed so
that the maximum depth y (mm) is less than the maximum depth x
(mm). The maximum depth x of the sipe 11 is preferably from 3 mm to
8 mm. A sipe width W of the sipe 11 is substantially constant in a
range from an end portion 121 located on the inner side of the
chamfered portion 12 in the tire radial direction to the groove
bottom of the sipe 11. In a configuration in which a protrusion is
disposed on the groove wall of the sipe 11, for example, the sipe
width W does not include the height of the protrusion. Also, in a
configuration in which the sipe width of the sipe 11 gradually
narrows toward the groove bottom, the width of the sipe 11 is
substantially measured as the sipe width not including the narrow
portion.
[0043] In the pneumatic tire described above, for all of the
chamfered portions, including at least the chamfered portions 12 of
the sipes 11, formed on grooves other than the main grooves 9, a
total projected area A.sub.IN of all the chamfered portions located
on the vehicle mounting inner side and a total projected area
A.sub.OUT of all the chamfered portions located on the vehicle
mounting outer side satisfy the relationship A.sub.IN>A.sub.OUT.
In the embodiment of FIG. 2, since only the sipes 11 are provided
with a chamfered portion, all of the chamfered portions formed on
grooves other than the main grooves 9 (the sipes 11 and the lug
grooves 200) are configured by the chamfered portions 12, and the
total projected area A.sub.OUT of all the chamfered portions 120C
located on the vehicle mounting outer side is less than the total
projected area A.sub.IN of all the chamfered portions 120A, 120B
located on the vehicle mounting inner side. Thus, as a method for
making the total projected area A.sub.OUT of all the chamfered
portions located on the vehicle mounting outer side less than the
total projected area A.sub.IN of all the chamfered portions located
on the vehicle mounting inner side, the total number of the sipes
11 located on the vehicle mounting outer side can be made less than
the total number of the sipes 11 located on the vehicle mounting
inner side, a chamfered portion can be provided on a groove in
addition to the sipe 11 (for example, a sipe or a lug groove)
located on the vehicle mounting inner side, and the like. Also, as
illustrated in FIG. 7, the total number of sipes 11 can be the same
on the vehicle mounting inner side and the vehicle mounting outer
side and the shape of the chamfered portions 12 of the sipes 11 can
be vastly different on the vehicle mounting inner side and the
vehicle mounting outer side, and the total projected area of the
chamfered portions 12 of the sipes 11 located on the vehicle
mounting outer side can be made relatively small, and the
relationship A.sub.IN>A.sub.OUT can be satisfied.
[0044] As illustrated in FIG. 7, the tread portion 1 is defined by
four main grooves 9 that extend in the tire circumferential
direction and includes the center rib 100A located on the tire
center line CL, the pair of intermediate ribs 100B, 100C located
outward of the center rib 100A in the tire lateral direction, and
the pair of shoulder ribs 100D, 100E located outward of the
intermediate ribs 100B, 100C in the tire lateral direction. Grooves
are not formed in the center rib 100A, the sipes 110B, 110C
including the chamfered portions 120B, 120C are formed in the
intermediate ribs 100B, 100C, respectively, and the lug grooves
200A, 200B are formed in the shoulder ribs 100D, 100E,
respectively. Additionally, the chamfered portions 120B, 120C have
an outer edge profile line that is not parallel with the ridge line
of the sipes 110B, 110C, the chamfered portion 120B increases in
width from the center side of the rib 10 toward the main groove 9
side, and the chamfered portion 120C decreases in width from the
center side of the rib 10 toward the main groove 9 side.
Furthermore, since chamfered portions are provided only in the
sipes 11, all of the chamfered portions formed on the grooves other
than the main grooves 9 (the sipes 11 and the lug grooves 200) are
constituted by the chamfered portions 120B, 120C. That is, the
total projected area A.sub.IN of all the chamfered portions 120B
located on the vehicle mounting inner side and the total projected
area A.sub.OUT of all the chamfered portions 120C positioned on the
vehicle mounting outer side satisfy the relationship
A.sub.IN>A.sub.OUT.
[0045] In the pneumatic tire described above, the chamfered portion
12 that is shorter than the sipe length L of the sipe 11 is
provided on each of the edge 11A on the leading side and the edge
11B on the trailing side of the sipe 11, and the non-chamfered
regions 13 in which other chamfered portions are not present, are
disposed at the portions facing the chamfered portions 12 of the
sipe 11. Thus, the drainage effect can be improved with the
chamfered portions 12, and a water film can be effectively removed
by the edge effect in the non-chamfered regions 13 in which the
chamfered portion 12 is not provided. As a result, the steering
stability performance on wet road surfaces can be greatly improved.
Moreover, the chamfered portion 12 and the non-chamfered region 13
in which chamfered portions are not present, are disposed alongside
each other on the edge 11A on the leading side and the edge 11B on
the trailing side in this manner. Thus, the effect of enhancing wet
performance as described above when braking and driving can be
maximally achieved. Furthermore, the vehicle mounting outer side is
a large contributor to noise performance. Thus, for all the
chamfered portions, including at least the chamfered portions 12 of
the sipes 11, which are chamfered portions formed on grooves other
than the main grooves 9, by the total projected area A.sub.OUT of
the chamfered portions located on the vehicle mounting outer side
being relatively small, the ground contact pressure on the vehicle
mounting outer side can be reduced, which leads to a reduction in
noise generated when running. As a result, the steering stability
performance on dry road surfaces, the steering stability
performance on wet road surfaces, and noise performance can be
enhanced in a well-balanced manner.
[0046] In the pneumatic tire described above, the maximum depth x
(mm) and the maximum depth y (mm) preferably satisfy the
relationship of Formula (1) below. By providing the sipes 11 and
the chamfered portions 12 so as to satisfy the relationship of
Formula (1) below, compared to a known chamfered sipe, the
chamfered area can be minimized, so the steering stability
performance on dry road surfaces can be improved. As a result, the
steering stability performance on dry road surfaces and the
steering stability performance on wet road surfaces can be improved
in a compatible manner. Here, when y<x.times.0.1 is true, the
drainage effect from the chamfered portions 12 is insufficient, and
when y>x.times.0.3+1.0 is true, the rigidity of the rib 10 is
reduced, leading to a reduction in the steering stability
performance on dry road surfaces. In particular, the relationship
y.ltoreq.x.times.0.3+0.5 is preferably satisfied.
x.times.0.1.ltoreq.y.ltoreq.x.times.0.3+1.0 (1)
[0047] For the all chamfered portions, the total projected area
A.sub.IN of the chamfered portions located on the vehicle mounting
inner side and the total projected area A.sub.OUT of the chamfered
portions located on the vehicle mounting outer side preferably
satisfy the following Formula (2). More preferably, the range is
from 10% to 30%. By setting the total projected area difference
between the total projected area A.sub.IN of the chamfered portions
on the vehicle mounting inner side and the total projected area
A.sub.OUT of the chamfered portions on the vehicle mounting outer
side in this manner, an effect of suppressing noise can be
obtained, and both the steering stability performance on dry road
surfaces and the steering stability performance on wet road
surfaces can be enhanced.
3%.ltoreq.(A.sub.IN-A.sub.OUT)/A.sub.IN.times.100%.ltoreq.50%
(2)
[0048] In the pneumatic tire described above, the sipes 11 are
preferably disposed in two or more ribs 10 of the plurality of ribs
10 defined by the main grooves 9. With the sipes 11 being disposed
in two or more of the ribs 10 in this manner, the steering
stability performance on dry road surfaces and the steering
stability performance on wet road surfaces can be enhanced in a
well-balanced manner.
[0049] In particular, all the chamfered portions including at least
the chamfered portions 12 of the sipes 11, which are chamfered
portions formed on grooves other than the main grooves 9, are
preferably configured by the chamfered portion 12 of the sipe 11.
In such a case, the total projected area difference
(A.sub.IN-A.sub.OUT) between the total projected area A.sub.IN of
all the chamfered portions on the vehicle mounting inner side and
the total projected area A.sub.OUT of all the chamfered portions on
the vehicle mounting outer side is equal to the total projected
area difference (A.sub.IN'-A.sub.OUT') between the total projected
area A.sub.IN' of the chamfered portions 12 of the sipes 11 on the
vehicle mounting inner side and the total projected area A.sub.OUT'
of the chamfered portions 12 of the sipes 11 on the vehicle
mounting outer side. With all of the chamfered portions described
above being configured by only the chamfered portion 12 in this
manner, the steering stability performance on dry road surfaces and
the steering stability performance on wet road surfaces can be
enhanced in a well-balanced manner.
[0050] FIG. 8 is a diagram illustrating another modified example of
a sipe and chamfered portions thereon formed in the tread portion
of a pneumatic tire according to an embodiment of the present
technology. The sipe 11 illustrated in FIG. 8 is formed with an
inclination angle .theta. with respect to the tire circumferential
direction. This inclination angle .theta. refers to the angle
formed by an imaginary line (the dotted line illustrated in FIG. 8)
connecting both end portions of the sipe 11 and the side surface of
the block 101. The inclination angle .theta. has an inclination
angle on the acute angle side and an inclination angle on the
obtuse angle side. In FIG. 8, the inclination angle .theta. on the
acute angle side is illustrated. The inclination angle .theta. is
the inclination angle of the sipe 11 at the intermediate pitch
within the rib 10. Here, the inclination angle .theta. on the acute
angle side is preferably from 40.degree. to 80.degree., and more
preferably from 50.degree. to 70.degree.. With the sipe 11 being
inclined with respect to the tire circumferential direction in this
way, pattern rigidity can be improved, and the steering stability
performance on dry road surfaces can be further improved. Here,
when the inclination angle .theta. is less than 40.degree., uneven
wear resistance performance is degraded. When the inclination angle
.theta. exceeds 80.degree., pattern rigidity cannot be sufficiently
improved.
[0051] In an embodiment of the present technology, the side having
the inclination angle .theta. on the acute angle side of the sipe
11 is defined as the acute angle side, and the side having the
inclination angle .theta. on the obtuse angle side of the sipe 11
is defined as the obtuse angle side. The chamfered portions 12A,
12B formed on the edges 11A, 11B of the sipe 11 are formed on the
acute angle side of the sipe 11. With the sipe 11 being chamfered
on the acute angle side in this manner, uneven wear resistance
performance can be further enhanced. Alternatively, the chamfered
portions 12A, 12B may be formed on the obtuse angle side of the
sipe 11. With the chamfered portion 12 being formed on the obtuse
angle side of the sipe 11 in this manner, the edge effect is
increased, and the steering stability performance on wet road
surfaces can be further improved.
[0052] In an embodiment of the present technology, the overall
shape of the sipe 11 described above is curved, allowing the
steering stability performance on wet road surfaces to be improved.
However, a portion of the sipe 11 may have a curved or bent shape
in a plan view. With the sipe 11 being formed in this manner, the
total amount of edges 11A, 11B of the sipes 11 is increased, and
the steering stability performance on wet road surfaces can be
improved.
[0053] As illustrated in FIG. 8, one chamfered portion 12 is
disposed on each of the edge 11A on the leading side and the edge
11B on the trailing side of the sipe 11. With the chamfered
portions 12 being disposed in this manner, uneven wear resistance
performance can be improved. Here, when two or more chamfered
portions 12 are formed in each of the edge 11A on the leading side
and the edge 11B on the trailing side of the sipe 11, the number of
nodes increases, which tends to deteriorate uneven wear resistance
performance.
[0054] The maximum width of the chamfered portion 12 measured in
the direction orthogonal to the sipe 11 is defined as a width W1.
The maximum width W1 of the chamfered portion 12 is preferably from
0.8 times to 5.0 times the sipe width W of the sipe 11, and more
preferably from 1.2 times to 3.0 times. With the maximum width W1
of the chamfered portion 12 being appropriately set with respect to
the sipe width W in this manner, the steering stability performance
on dry road surfaces and the steering stability performance on wet
road surfaces can be improved in a compatible manner. When the
maximum width W1 of the chamfered portion 12 is less than 0.8 times
the sipe width W of the sipe 11, the steering stability performance
on wet road surfaces cannot be sufficiently improved, and when the
maximum width W1 is greater than 5.0 times the sipe width W, the
steering stability performance on dry road surfaces cannot be
sufficiently improved.
[0055] Furthermore, the outer edge portion in the longitudinal
direction of the chamfered portion 12 is formed parallel with the
extension direction of the sipe 11. With the chamfered portion 12
extending parallel with the sipe 11 in this way, uneven wear
resistance performance can be improved, and the steering stability
performance on dry road surfaces and the steering stability
performance on wet road surfaces can be improved in a compatible
manner.
[0056] As illustrated in FIG. 8, end portions of the chamfered
portions 12A, 12B located near the main grooves 9 communicate with
the main grooves 9 located on either side of the rib 10. With the
chamfered portions 12A, 12B being formed in this manner, the
steering stability performance on wet road surfaces can be further
improved. Alternatively, the end portions of the chamfered portions
12A, 12B located near the main grooves 9 may terminate within the
rib 10 without communicating with the main grooves 9. With the
chamfered portions 12A, 12B being formed in this manner, the
steering stability performance on dry road surfaces can be further
improved.
[0057] FIGS. 9A and 9B are diagrams illustrating another modified
example of a sipe and chamfered portions thereon formed in the
tread portion of a pneumatic tire according to an embodiment of the
present technology. As illustrated in FIG. 9A, the chamfered
portion 12A and the chamfered portion 12B are formed so that a
portion of both of the chamfered portions 12A, 12B overlap in a
central portion of the sipe 11. Here, the length in the tire
lateral direction of the overlapping portion, which is a portion
where the chamfered portion 12A and the chamfered portion 12B
overlap, is defined as an overlap length L1. On the other hand, as
illustrated in FIG. 9B, when a portion of both the chamfered
portion 12A and the chamfered portion 12B do not overlap and are
separated by a certain interval, the proportion of the overlap
length L1 with respect to the sipe length L is expressed as a
negative value. The overlap length L1 of the overlapping portion is
preferably from -30% to 30% of the sipe length L, and more
preferably from -15% to 15%. With the overlap length L1 of the
chamfered portion 12 being appropriately set with respect to the
sipe length L in this manner, the steering stability performance on
dry road surfaces and the steering stability performance on wet
road surfaces can be improved in a compatible manner. Here, when
the overlap length L1 is greater than 30%, the steering stability
performance on dry road surfaces is not sufficiently improved, and
when the overlap length L1 is less than -30%, the steering
stability performance on wet road surfaces is not sufficiently
improved.
[0058] FIG. 10 is a view of the sipe cut away in the extension
direction. As illustrated in FIG. 10, the sipe 11 includes a raised
bottom portion 14 in a portion of the sipe 11 in the length
direction. As the raised bottom portion 14, a raised bottom portion
14A located in the central portion of the sipe 11 and raised bottom
portions 14B located at both end portions of the sipe 11 are
present. By providing the raised bottom portion 14 in the sipe 11
in this manner, the steering stability performance on dry road
surfaces and the steering stability performance on wet road
surfaces can be improved in a compatible manner. The raised bottom
portion 14 of the sipe 11 may be formed at the end portion and/or
not at the end portion of the sipe 11.
[0059] The height in the tire radial direction of the raised bottom
portion 14 formed in the sipe 11 is defined as a height H.sub.14.
For the raised bottom portion 14A formed not at the end portion of
the sipe 11, the maximum height from the groove bottom of the sipe
11 to the top surface of the raised bottom portion 14A is defined
as a height H.sub.14A. The height H.sub.14A is preferably from 0.2
times to 0.5 times the maximum depth x of the sipe 11, and more
preferably from 0.3 times to 0.4 times. By setting the height
H.sub.14A of the raised bottom portion 14A disposed not at the end
portion of the sipe 11 to a suitable height, the rigidity of the
block 101 can be improved and the drainage effect can be
maintained. As a result, the steering stability performance on wet
road surfaces can be improved. Here, when the height H.sub.14A is
less than 0.2 times the maximum depth x of the sipe 11, the
rigidity of the block 101 cannot be sufficiently improved, and when
the height H.sub.14A is greater than 0.5 times the maximum depth x
of the sipe 11, the steering stability performance on wet road
surfaces cannot be sufficiently improved.
[0060] For the raised bottom portions 14B formed at both end
portions of the sipe 11, the maximum height from the groove bottom
of the sipe 11 to the top surface of the raised bottom portion 14B
is defined as a height H.sub.14B. The height H.sub.14B is
preferably from 0.6 times to 0.9 times the maximum depth x of the
sipe 11, and more preferably from 0.7 times to 0.8 times. By
setting the height H.sub.14B of the raised bottom portions 14B
disposed at the end portions of the sipe 11 to a suitable height,
the rigidity of the block 101 can be improved and the steering
stability performance on dry road surfaces can be improved. Here,
when the height H.sub.14B is less than 0.6 times the maximum depth
x of the sipe 11, the rigidity of the block 101 cannot be
sufficiently improved, and when the height H.sub.14B is greater
than 0.9 times the maximum depth x of the sipe 11, the steering
stability performance on wet road surfaces cannot be sufficiently
improved.
[0061] The length in the tire lateral direction of the raised
bottom portion 14 of the sipe 11 is defined as a raised bottom
length L.sub.14. The raised bottom lengths L.sub.14A, L.sub.14B of
the raised bottom portions 14A, 14B is preferably from 0.3 times to
0.7 times the sipe length L, and more preferably from 0.4 times to
0.6 times. By the raised bottom lengths L.sub.14A, L.sub.14B of the
raised bottom portions 14A, 14B being appropriately set in this
manner, the steering stability performance on dry road surfaces and
the steering stability performance on wet road surfaces can be
improved in a compatible manner.
Examples
[0062] Tires according to a Conventional Example 1, 2 and Examples
1 to 5 were manufactured. The tires have a tire size of 245/40R19
and a designated mounting direction with respect to a vehicle and
include, in a tread portion, main grooves extending in the tire
circumferential direction, ribs defined by the main grooves, and
sipes extending in the tire lateral direction in the ribs. The
tires are set as indicated in Table 1 for the following: chamfer
arrangement (both sides or one side), size relationship between
sipe length L and chamfer lengths L.sub.A, L.sub.B, chamfer
provided at portion facing chamfered portion, size relationship
between total projected area A.sub.IN of all chamfered portions on
the vehicle mounting inner side and total projected area A.sub.OUT
of all chamfered portions on the vehicle mounting outer side, sipe
width, total projected area difference between all chamfered
portions on vehicle mounting inner side and all chamfered portions
on vehicle mounting outer side
((A.sub.IN-A.sub.OUT)/A.sub.IN.times.100%), the number of ribs with
sipes including chamfered portions, and total projected area
difference between chamfered portions of sipes on the vehicle
mounting inner side and chamfered portions of sipes on the vehicle
mounting outer side
((A.sub.IN'-A.sub.OUT')/A.sub.IN'.times.100%).
[0063] Note that in Table 1, when the value of the "total projected
area difference between all chamfered portions on vehicle mounting
inner side and all chamfered portions on vehicle mounting outer
side" is the same as the value of the "total projected area
difference between chamfered portions of sipes on vehicle mounting
inner side and chamfered portions of sipes on vehicle mounting
outer side", this means that all the chamfered portions including
at least the chamfered portions of the sipes, which are chamfered
portions formed on grooves other than main grooves, are configured
by the chamfered portion of the sipe.
[0064] These test tires underwent a sensory evaluation by a test
driver for steering stability performance on dry road surfaces and
steering stability performance on wet road surfaces and a sensory
evaluation for noise performance. The results thereof are shown in
Table 1.
[0065] Sensory evaluation for steering stability performance on dry
road surfaces and steering stability performance on wet road
surfaces was performed with the test tires on a wheel with a rim
size of 19.times.8.5 J mounted on a vehicle and inflated to an air
pressure of 260 kPa. Evaluation results are expressed as index
values, with the results of Conventional Example 1 being assigned
as an index value of 100. Larger index values indicate superior
steering stability performance on dry road surfaces and steering
stability performance on wet road surfaces.
[0066] The sensory evaluation for noise performance was performed
with the test tires on a wheel with a rim size of 19.times.8.5 J
mounted on a vehicle and inflated to an air pressure of 260 kPa.
Evaluation results are expressed as index values, with the results
of Conventional Example 1 being assigned as an index value of 100.
Larger index values indicate superior noise performance.
TABLE-US-00001 TABLE 1-1 Conven- Conven- tional tional Exam-
Example 1 Example 2 ple 1 Chamfer arrangement (both sides or Both
One Both one side) sides side sides Size relationship between sipe
length L = L.sub.A, L= L.sub.A L > L.sub.A, L and chamfer
lengths L.sub.A, L.sub.B L.sub.B L.sub.B Chamfer provided at
portion facing Yes No No chamfered portion Size relationship
between total A.sub.IN = A.sub.IN = A.sub.IN > projected area
A.sub.IN of all chamfered A.sub.OUT A.sub.OUT A.sub.OUT portions on
vehicle mounting inner side and total projected area A.sub.OUT of
all chamfered portions on vehicle mounting outer side Sipe width
Constant Changes Changes Total projected area difference 0% 0% 3%
between all chamfered portions on vehicle mounting inner side and
all chamfered portions on vehicle mounting outer side ((A.sub.IN -
A.sub.OUT)/A.sub.IN .times. 100%) dumber of ribs with sipes
including 1 1 1 chamfered portions Total projected area difference
0% 0% 3% between chamfered portions of sipes on vehicle mounting
inner side and chamfered portions of sipes on vehicle mounting
outer side ((A.sub.IN' - A.sub.OU')/A.sub.IN' .times. 100%)
Steering stability performance on dry 100 90 105 road surfaces
Steering stability performance on wet 100 105 105 road surfaces
Noise performance 100 100 102
TABLE-US-00002 TABLE 1-2 Exam- Exam- Exam- Exam- ple 2 ple 3 ple 4
ple 5 Chamfer arrangement (both sides Both Both Both Both or one
side) sides sides sides sides Size relationship between sipe L >
L.sub.A, L > L.sub.A, L > L.sub.A, L > L.sub.A, length L
and chamfer lengths L.sub.A, L.sub.B L.sub.B L.sub.B L.sub.B
L.sub.B Chamfer provided at portion No No No No facing chamfered
portion Size relationship between total A.sub.IN > A.sub.IN >
A.sub.IN > A.sub.IN > projected area A.sub.IN of all
A.sub.OUT A.sub.OUT A.sub.OUT A.sub.OUT chamfered portions on
vehicle mounting inner side and total projected area A.sub.OUT of
all chamfered portions on vehicle mounting outer side Sipe width
Con- Con- Con- Con- stant stant stant stant Total projected area
difference 3% 20% 20% 20% between all chamfered portions on vehicle
mounting inner side and all chamfered portions on vehicle mounting
outer side ((A.sub.IN - A.sub.OUT)/A.sub.IN .times. 100%) dumber of
ribs with sipes 1 1 3 3 including chamfered portions Total
projected area difference 3% 3% 3% 20% between chamfered portions
of sipes on vehicle mounting inner side and chamfered portions of
sipes on vehicle mounting outer side ((A.sub.IN' -
A.sub.OU')/A.sub.IN' .times. 100%) Steering stability performance
on 106 107 108 109 dry road surfaces Steering stability performance
on 106 107 108 109 wet road surfaces Noise performance 102 102 104
104
[0067] As can be seen from Table 1, by devising the shape of the
chamfered portions formed on the sipes, the tires of Examples 1 to
5 have enhanced noise performance and both enhanced steering
stability performance on dry road surfaces and enhanced steering
stability performance on wet road surfaces.
* * * * *